The journey of a generation: advances and promises in the study of primordial germ cell migration

Abstract

The germline provides the genetic and non-genetic information that passes from one generation to the next. Given this important role in species propagation, egg and sperm precursors, called primordial germ cells (PGCs), are one of the first cell types specified during embryogenesis. In fact, PGCs form well before the bipotential somatic gonad is specified. This common feature of germline development necessitates that PGCs migrate through many tissues to reach the somatic gonad. During their journey, PGCs must respond to select environmental cues while ignoring others in a dynamically developing embryo. The complex multi-tissue, combinatorial nature of PGC migration is an excellent model for understanding how cells navigate complex environments in vivo. Here, we discuss recent findings on the migratory path, the somatic cells that shepherd PGCs, the guidance cues somatic cells provide, and the PGC response to these cues to reach the gonad and establish the germline pool for future generations. We end by discussing the fate of wayward PGCs that fail to reach the gonad in diverse species. Collectively, this field is poised to yield important insights into emerging reproductive technologies.

A positive feedback loop between germ cells and gonads induces and maintains cnidarian sexual reproduction

“…Their respective developmental origin, however, is spatially and temporally distinct. In most animals, germ cells are generated only once in a lifetime during early embryonic development 1,2 . Somatic gonad tissues develop later and are derived from mesoderm.…”

“…Somatic gonad tissues develop later and are derived from mesoderm. Once specified, primordial germ cells migrate to the region of developing gonads where they are incorporated with somatic gonad cells 2,3 . Defects in integration result in impaired fertility 4 .…”